The pursuit of flat movements is a constant preoccupation of the horological industry. This is in response to a permanent market demand. The object is also to be able to house mechanisms relating to different complications or functions more easily, and/or in a larger number, within the same timepiece, while retaining control of the overall thickness of the timepiece.
In a conventional mechanical movement, the energy stored in the barrel is generally transmitted to a centre-wheel. This centre-wheel meshes with a third wheel pinion. The third-wheel pinion has a dual function. On the one hand, it drives a fourth-wheel pinion, via a third-wheel secured to the third wheel pinion. The fourth-wheel pinion is integral with a seconds wheel, which meshes with the escape pinion and thus cooperates with the escape wheel and the regulating assembly for regulating the movement. The same fourth-wheel pinion is also integral with an arbour carrying a seconds hand or meshes with an arbour of this type. The other function of the third-wheel pinion is to indirectly drive both the cannon-pinion and the associated hand, and the hour wheel and the associated hour hand.
The motion work must be able to be disconnected in order to ensure normal operation in the connected position and to set the time in the disconnected position. The disconnecting mechanism generally relies on a friction mechanism.
The mechanism for indirectly driving the minute cannon-pinion and the hour wheel generally includes a friction plate which is coaxial to the cannon-pinion.
In order to drive the minute cannon-pinion, the third wheel pinion meshes with the friction plate. The friction thereof on the cannon-pinion causes the latter to pivot.
To drive the hours, the third wheel pinion again meshes with the friction plate, and the cannon-pinion driven by said plate meshes with a minute wheel, integral with a minute pinion which meshes with the hour wheel.
This tried and tested mechanism operates well, but requires a certain amount of space, particularly due to the presence of the friction plate and a surface for holding the plate on the cannon-pinion, on the opposite side to the hands. For a wristwatch, this space requirement is on the order of 0.25 to 0.35 mm, which is significant with respect to the total thickness of the movement, which is usually several millimeters, or a millimeter in extra-flat calibres such as, for example, the “Fréderic Piguet” 21 calibre, which is 1.73 mm thick. The proportion taken up by the friction plate and its holding surface is thus large, since it may represent 5 to 25% of the total thickness of a movement.
Some decentred centre-wheel embodiments have proposed different solutions for the friction plate described above.
CH Patent 377 727 in the name of Buren Watch Company, relates to a timepiece with a decentred centre-wheel which, to overcome the problem of fluttering hands in a watch with indirect driving of the minute hand, or in a “Roskopf” watch, implements a flexible minute wheel, which is stressed and whose elasticity compensates for the fluttering of the hands. In a first version, the barrel drives a centre-wheel, on which an indented intermediate wheel is mounted, which in turn drives the minute wheel, which meshes in a conventional manner with the minute and hour cannon-pinions. The centre-wheel drives a third wheel set which meshes with a fourth wheel set, which in turn meshes with the escape pinion. To set the time, the indented intermediate wheel meshes with an intermediate set hands wheel connected to the crown arbour. In a second version suited to a “Roskopf” watch, the minute wheel is sliding friction tight directly to the barrel, and meshes in a conventional manner with the minute and hour cannon-pinions. A complementary gear train, of the centre-wheel set and third wheel set type, is necessary to drive the fourth wheel set. However, in this second version, the superposition of the wheels on the barrel does not assist in decreasing the thickness of the movement.
EP Patent No. 1 243 985 in the name of Widerrecht discloses a watch movement with a central orifice, ensuring an annular arrangement of the various functions, but to the detriment of the thickness of the movement. The hour and minute cannon-pinions are tubular and at the periphery of the central orifice. As all of the gear trains have to be housed in the remaining annular volume, a particular arrangement concerns the connection between the centre-wheel set, driven by the barrel, and the minute wheel set. The centre-pinion is engaged in the bottom plate of the watch, and includes a pivot-shank, on which the minute wheel set is mounted via its pinion, which has an indentation cooperating with the pivot-shank to provide a friction coupling. Thus, the minute wheel set rotates with the centre-wheel set, except during time-setting, when it slides over the pivot-shank due to the friction coupling. However, the diameter of the motion work is necessarily limited by the particular construction, which hinders the play in such gears.
CH Patent Application No. 14 525 A in the name of EMILE JERGER discloses a Roskopf watch which has a movement with a power reserve of eight days and a barrel of large height. The intermediate minute wheel is placed on the axis of the first centre-pinion meshing with the barrel, and is sliding friction tight on a pipe of a wheel controlling the escape mechanism.
FR Patent No. 1 181 584 in the name of RENAUDIN discloses a mechanism with a single operating button, of parallel axis to the arbours of the movement. The toothed crown of its barrel meshes with a pinion mounted on a minute arbour, and carries a toothed wheel normally driven by the minute arbour, but which can also rotate with respect to said arbour to control the setting of the hands.
CH Patent Application No. 54 708A in the name of MAIRE-FAVRE discloses a movement with a long running time, which also includes a minute wheel fitted friction tight to a cylindrical shoulder of a wheel integral with the arbour, controlled by the barrel core toothing.
CH Patent Application No. 51 982A in the name of MARC DUBOIS discloses a decentred barrel mechanism with a barrel core carrying a wheel meshing with the going train and which controls the escape mechanism. The first wheel set of the going train includes a friction tight fitted intermediate wheel, which meshes with the intermediate set-hands wheel and with a wheel wedged on a set-hands arbour which is freely housed in the core axis and indirectly actuates the hour and minute hands.
However, these mechanisms have the drawback of juxtaposing the thickness of a barrel with that of a centre-wheel, which is not conducive to the desired reduction in thickness.
The invention proposes to allow the motion work to be uncoupled while occupying the smallest possible thickness. Reducing the space required for the transmission of motion from a gear train wheel, directly or indirectly connected to the barrel, to the cannon-pinion on the one hand and to the hour wheel on the other hand, through the motion work, immediately reduces the general space requirement of the movement.
The invention therefore concerns a timepiece gear train device of reduced height with a large power reserve, comprising at least one means of energy storage, arranged to be powered by a motion imparted to the winding stem and/or to an oscillating weight, said energy storage means comprising at least one barrel, and said gear train device driving display means which include at least one cannon-pinion and one hour wheel driven directly about a main pivot axis by a motion work, said gear train device comprising, driven directly or indirectly by said at least one barrel, at least one driving wheel pivoting about a secondary pivot axis external to said at least one barrel, and said driving wheel being friction coupled to said motion work on a friction surface coaxial to said secondary pivot axis of said driving wheel, and said main pivot axis being secant to said at least one barrel, characterized in that said driving wheel includes a driving cannon-pinion pivoting about a wheel body along said secondary pivot axis and connected to a shoulder of said wheel body which forms said friction surface by a friction means formed by a friction spring, and in that said driving cannon-pinion cooperates with a minute wheel belonging to said motion work and pivoting about a minute axis.
According to a feature of the invention, said gear train device includes a bottom plate carrying wheel sets comprised in said device, said bottom plate including a first surface called the dial side surface and a second surface called the gear train side surface which are opposite to each other and connected by a peripheral edge, and said main pivot axis is located in proximity to the centre of or at the centre of said bottom plate, and the diameter of said at least one barrel, which pivots about a barrel pivot axis substantially parallel to said main pivot axis and to said secondary pivot axis, which are parallel to each other, covers an area, about said barrel pivot axis, which is greater than the smallest distance between said main pivot axis and said peripheral edge.
According to a feature of the invention, said cannon-pinion and said hour wheel project from the side of said first surface and said at least one barrel is arranged on said second surface, or vice versa.
According to a feature of the invention, said cannon-pinion meshes with a plate comprised in said minute wheel, and said hour wheel meshes with a pinion integral with said plate.
According to a feature of the invention, said driving wheel is a centre-wheel which comprises, integral with each other and with a wheel body, on the one hand a pinion which is external to said at least one barrel and meshes directly or indirectly with a drum toothing comprised in said at least one barrel, and on the other hand a plate meshing with a third wheel, which in turn meshes with a main seconds arbour pivoting about said main pivot axis coaxially to said cannon-pinion and to said hour wheel, in a centre tube.
According to a feature of the invention, the smallest diameter of said friction surface is greater than the largest pivoting guide diameter of said driving wheel with respect to a bottom plate comprised in said device.
The invention further concerns a gear train module comprising at least one gear train device of this type with a bottom plate of this type, and which comprises a means of interface with external means of adjusting said motion work.
According to a feature of the invention, said gear train module includes a means of interface with external means of powering said energy storage means including at least one barrel.
The invention further concerns a timepiece movement including at least one gear train device and/or at least one gear train module of this type, and which includes external means of adjusting said motion work cooperating with interface means comprised in said gear train device.
According to a feature of the invention, said timepiece movement includes external means of powering said energy storage means including at least one barrel cooperating with interface means comprised in said gear train device.
The invention also concerns a timepiece including at least one timepiece movement of this type and/or at least one gear train device of this type and/or at least one gear train module of this type, which is a watch and includes at least one barrel, whose diameter is larger than half the smallest dimension of said watch in a plane perpendicular to said main pivot axis.
The invention dispenses with the need for the known large diameter cannon-pinions of the prior art.
With the mechanism of the invention, there is no fourth wheel with a pinion plate, just a very small pinion. This small pinion preferably cooperates with an intermediate wheel, which cooperates with a small seconds wheel placed elsewhere in the movement.
The advantage is being able to position the seconds display as desired, either in a small seconds position or with the centre seconds.
The going train is taut, which ensures that play is permanently taken up in the movement. This situation should be compared to the conventional small seconds configuration which starts from the escape wheel, where the gear train is not taut, and the gear set requires the implementation of a spring, which is detrimental to efficiency.
It is one of the objects of the invention to maximise the volume of the barrel or barrels, so as to increase as much as possible the operating autonomy of the timepiece and possibly its additional high energy consuming functions, such as striking works, alarms or similar. The increase in stored energy may also allow the use, for some functions, of low yield technologies with very low production costs, which reduces the manufacturing cost of the timepiece but provides equivalent or better operating performance.
In a conventional configuration of the prior art, the seconds wheel passes through the entire thickness of the movement, and the maximum possible barrel diameter is then necessarily smaller than the smallest radius of the timepiece or watch.
The configuration according to the invention however allows the dimensions of the barrel diameter to be greater than the watch radius with a passage beyond the centre. Consequently, the thickness of the movement at the centre of the timepiece must be sized in a draconian manner in order to allow the barrel to be accommodated.